A. Field of the Invention
The present invention relates to a new and improved drilling machine for tapping high pressure pipeline systems and, more particularly, to a new and improved drilling machine that can be operated at a controlled drilling rate by one person.
B. Description of the Background Art
It is often necessary to tap a high pressure pipeline to provide access for another user. It is preferable in these circumstances to perform the tapping operation without shutdown of the pipeline system.
Tapping of high pressure pipelines is typically accomplished by a drilling machine that is manually operated by a minimum of two people, or operated by a pneumatic drive also requiring two people for operation. Two operators are necessary because two separate operations are performed. The first operation involves rotating a drill. While the drill is being rotated, it must also be advanced through the wall of the pipe at a controlled rate. This requires a second operation involving rotating a feed tube at a different rate of rotation in order to advance the drill into the pipeline.
One existing drilling machine requires an operator to rotate a ratchet crank to rotate the drill while a second operator tightens a friction band type clutch coupling the rotation of the crank to the feed tube. Such a clutch arrangement has the disadvantage that the rotation of the drill must be stopped each time the clutch is adjusted.
Another existing drilling machine employs a clutch defined by a clutch member and a clutch disc with a friction disc between them. The friction disc is fabricated from a graphite impregnated Nylon such as Nylontron and the surfaces of the clutch member and clutch disc abutting the friction disc are smooth. If gas pressure in the pipeline being tapped is high, the pressure makes the drill more difficult to advance, and the smooth surfaces allow slippage preventing advancement of the drill.